The present invention relates to a vehicle having two wheels, an engine which drives at least one of the wheels, a gearbox, a frame connected to the engine and two front and rear suspension arms of the pivotal type.
A vehicle is known which comprises driving wheels capable of being uncoupled and a device for adjusting the castor and the castor angle of the front wheel and is described in PCT/FR88/00073.
More particularly, in the case of the described vehicle having two wheels, two synchronous and distinct driving shafts are provided, one for rear wheel and the other for the front wheel. The suspensions are of the type having a pivotal arm and a pivot axis of each of these arms is distinct from the axis of the driving shafts. This makes it necessary for example in the case of a chain transmission, to require a tightener for compensating for the tension of the chain upon movements of the arm. Moreover, the weight of the different transmission elements is great. Also, reliability is reduced bearing in mind that the number of moving parts is large and the useful power may be reduced, in particular by losses due to friction.
Furthermore, the steering unit comprises a steering column driven in rotation at one end by a handlebar and connected at its other end to a compass system itself articulated to a front steering fork, the latter being fixed to an inner hub which is rotatably mounted to be steerable on a pin carried by a pivot connected to the pivotal arm.
In order to facilitate the steering orientation of the front wheel, the articulations are of the universal type, but this results in particular in an increase in weight, a reduction in handling and reliability, a higher cost and increased maintenance.